The invention concerns a shaft seal, in particular a radial shaft seal, with at least one sealing element of polyfluorocarbon, preferably polytetrafluoroethylene, that is provided with a sealing lip that is contacting a surface to be sealed under radial force action.
In shaft seals in the form of radial shaft seals, polyfluorocarbon, in particular polytetrafluoroethylene, is used as a material for the sealing elements because of its special physical and chemical properties. The sealing elements are embodied as annular disks whose radial inner area is elastically bent for forming the sealing lip. In case of polyfluorocarbons, in particular polytetrafluoroethylene, creeping can be observed. Moreover, these materials have a relatively minimal mechanical strength. Creeping of this material has the result that the sealing action decreases. In order to counteract this creeping action, the radial pretension that is acting on the sealing lip is therefore increased. This causes however a correspondingly greater wear of the sealing lip. In sealing applications, it is therefore difficult to find a balance between seal-tightness and wear.
In order to achieve this balance, it is known to add to the sealing element different fillers, for example, glass fibers, carbon fibers, bronze and the like. These additives however require a complex and expensive manufacture.
The invention has the object to configure the shaft seal of the aforementioned kind in such a way that its seal-tightness during its period of use is substantially maintained while its manufacture is constructively simpler and less expensive.